Cardiac disease treatment and device

ABSTRACT

A cardiac constraint device comprising a jacket of biological compatible material and an adjustment member. The jacket is adapted to be secured to the heart to snugly conform to an external geometry of the heart and assume a maximum adjusted volume to constrain circumferential expansion of the heart beyond the maximum adjusted volume during diastole and to permit unimpeded contraction of the heart during systole. The adjustment mechanism is configured to alter the internal volume defined by the jacket after the jacket is secured to the heart. The invention also provides a method for treating cardiac disease.

FIELD OF THE INVENTION

The present invention pertains to a device and method for treatingcongestive heart disease and related valvular dysfunction. Moreparticularly, the present invention is directed to a cardiac constraintthat is adjustable after implantation.

BACKGROUND OF THE INVENTION

Congestive heart disease is a progressive and debilitating illness. Thedisease is characterized by a progressive enlargement of the heart. Asthe heart enlarges, the heart is performing an increasing amount of workin order to pump blood each heart beat. In time, the heart becomes soenlarged the heart cannot adequately supply blood. An afflicted patientis fatigued, unable to perform even simple exerting tasks andexperiences pain and discomfort. Further, as the heart enlarges, theinternal heart valves cannot adequately close. This impairs the functionof the valves and further reduces the heart's ability to supply blood.

Causes of congestive heart disease are not fully known. In certaininstances, congestive heart disease may result from viral infections. Insuch cases, the heart may enlarge to such an extent that the adverseconsequences of heart enlargement continue after the viral infection haspassed and the disease continues its progressively debilitating course.

Patients suffering from congestive heart disease are commonly groupedinto four classes (i.e., Classes I, II, III and IV). In the early stages(e.g., Classes I and II), drug therapy is the commonly proscribedtreatment. Drug therapy treats the symptoms of the disease and may slowthe progression of the disease. Importantly, there is no cure forcongestive heart disease. Even with drug therapy, the disease willprogress. Further, the drugs may have adverse side effects.

Presently, the only permanent treatment for congestive heart disease isheart transplant. To qualify, a patient must be in the later stage ofthe disease (e.g., Classes III and IV with Class IV patients givenpriority for transplant). Such patients are extremely sick individuals.Class III patients have marked physical activity limitations and ClassIV patients are symptomatic even at rest.

Due to the absence of effective intermediate treatment between drugtherapy and heart transplant, Class III and IV patients will havesuffered terribly before qualifying for heart transplant. Further, aftersuch suffering, the available treatment is unsatisfactory. Hearttransplant procedures are very risky, extremely invasive and expensiveand only shortly extend a patient's life. For example, prior totransplant, a Class IV patient may have a life expectancy of 6 months toone-year. Heart transplant may improve the expectancy to about fiveyears.

Unfortunately, not enough hearts are available for transplant to meetthe needs of congestive heart disease patients. In the United States, inexcess of 35,000 transplant candidates compete for only about 2,000transplants per year. A transplant waiting list is about 8-12 monthslong on average and frequently a patient may have to wait about 1-2years for a donor heart. While the availability of donor hearts hashistorically increased, the rate of increase is slowing dramatically.Even if the risks and expense of heart transplant could be tolerated,this treatment option is becoming increasingly unavailable. Further,many patient's do not qualify for heart transplant for failure to meetany one of a number of qualifying criteria.

Congestive heart failure has an enormous societal impact. In the UnitedStates alone, about five million people suffer from the disease (ClassesI through IV combined). Alarmingly, congestive heart failure is one ofthe most rapidly accelerating diseases. (about 400,000 new patients inthe United States each year). Economic costs of the disease have beenestimated at $38 billion annually.

Not surprising, substantial effort has been made to find alternativetreatments for congestive heart disease. Recently, a new surgicalprocedure has been developed. Referred to as the Batista procedure, thesurgical technique includes dissecting and removing portions of theheart in order to reduce heart volume. This is a radical new andexperimental procedure subject to substantial controversy. Furthermore,the procedure is highly invasive, risky and expensive and commonlyincludes other expensive procedures (such as a concurrent heart valvereplacement). Also, the treatment is limited to Class IV patients and,accordingly, provides no hope to patients facing ineffective drugtreatment prior to Class IV. Finally, if the procedure fails, emergencyheart transplant is the only available option.

Clearly, there is a need for alternative treatments applicable to bothearly and later stages of the disease to either stop the progressivenature of the disease or more drastically slow the progressive nature ofcongestive heart disease. Unfortunately, currently developed options areexperimental, costly and problematic.

Cardiomyoplasty is a recently developed treatment for earlier stagecongestive heart disease (e.g., as early as Class III dilatedcardiomyopathy). In this procedure, the latissimus dorsi muscle (takenfrom the patient's shoulder) is wrapped around the heart and chronicallypaced synchronously with ventricular systole. Pacing of the muscleresults in muscle contraction to assist the contraction of the heartduring systole.

While cardiomyoplasty has resulted in symptomatic improvement, thenature of the improvement is not understood. For example, one study hassuggested the benefits of cardiomyoplasty are derived less from activesystolic assist than from remodeling, perhaps because of an externalelastic constraint. The study suggests an elastic constraint (i.e., anon-stimulated muscle wrap or an artificial elastic sock placed aroundthe heart) could provide similar benefits. Kass et al., ReverseRemodeling From Cardiomyoplasty In Human Heart Failure: ExternalConstraint Versus Active Assist, 91 Circulation 2314-2318 (1995).

Even though cardiomyoplasty has demonstrated symptomatic improvement,studies suggest the procedure only minimally improves cardiacperformance. The procedure is highly invasive requiring harvesting apatient's muscle and an open chest approach (i.e., sternotomy) to accessthe heart. Furthermore, the procedure is expensive—especially thoseusing a paced muscle. Such procedures require costly pacemakers. Thecardiomyoplasty procedure is complicated. For example, it is difficultto adequately wrap the muscle around the heart with a satisfactory fit.Also, if adequate blood flow is not maintained to the wrapped muscle,the muscle may necrose. The muscle may stretch after wrapping reducingits constraining benefits and is generally not susceptible topost-operative adjustment. Finally, the muscle may fibrose and adhere tothe heart causing undesirable constraint on the contraction of the heartduring systole. In addition to cardiomyoplasty, mechanical assistdevices have been developed as intermediate procedures for treatingcongestive heart disease. Such devices include left ventricular assistdevices (“LVAD”) and total artificial hearts (“TAH”). An LVAD includes amechanical pump for urging blood flow from the left ventricle and intothe aorta. An example of such is shown in U.S. Pat. No. 4,995,857 toArnold dated Feb. 26, 1991. TAH devices, such as the celebrated Jarvikheart, are used as temporary measures while a patient awaits a donorheart for transplant.

Other attempts at cardiac assist devices are found in U.S. Pat. No.4,957,477 to Lundbäck dated Sep. 18, 1990, U.S. Pat. No. 5,131,905 toGrooters dated Jul. 21, 1992 and U.S. Pat. No. 5,256,132 to Snydersdated Oct. 26, 1993. Both of the Grooters and Snyders patents teachcardiac assist devices which pump fluid into chambers opposing the heartto assist systolic contractions of the heart. The Lundbäck patentteaches a double-walled jacket surrounding the heart. A fluid fills achamber between the walls of the jacket. The inner wall is positionedagainst the heart and is pliable to move with the heart. Movement of theheart during beating displaces fluid within the jacket chamber.

Commonly assigned U.S. Pat. No. 5,702,343 to Alferness dated Dec. 30,1997 (corresponding to PCT Application WO 98/14136, published Apr. 9,1998) teaches a jacket to constrain cardiac expansion during diastole.The present invention pertains to improvements to the inventiondisclosed in the '343 patent.

SUMMARY OF THE INVENTION

According to a preferred embodiment of the present invention, a methodand device are disclosed for treating congestive heart disease andrelated cardiac complications such as valvular disorders. The inventionincludes a jacket of biologically compatible material. The jacket has aninternal volume dimensioned for an apex of the heart to be inserted intothe volume and for the jacket to be slipped over the heart. The jackethas a longitudinal dimension between upper and lower ends sufficient forthe jacket to surround a lower portion of the heart. Preferably, thejacket is configured to surround a valvular annulus of the heart and atleast the ventricular lower extremities of the heart. The jacket isadapted to be secured to the heart. The jacket is adjustable on theheart to snugly conform to an external geometry of the heart and assumea maximum adjusted volume for the jacket to constrain circumferentialexpansion of the heart beyond the maximum adjusted volume duringdiastole and to permit unimpeded contraction of the heart duringsystole.

The cardiac constraint device further comprises an adjustment mechanismconfigured to alter the internal volume defined by the jacket.Preferably the adjustment mechanism is configured to alter the internalvolume defined by the jacket after the jacket is secured to the heart.In one embodiment, the adjustment mechanism is configured to alter theinternal volume defined by the jacket by varying the thickness of thejacket material defining the internal volume, for example, byconstructing the jacket material at least in part from hygroscopicpolymer or by incorporating a balloon catheter into the cardiacconstraint device. Alternately, the adjustment mechanism may include aspecialized material, such as a biodegradable material, a stimulussensitive material, or a memory metal material. In another embodiment,the adjustment mechanism is configured to cinch the jacket material toeffectively decrease said internal volume defined by said jacket, forexample, using a stay element or a spring tensioning device.

The invention also provides a method for treating cardiac disease bysurgically accessing a patient's heart, placing a cardiac restrainingdevice around the patient's heart, adjusting the jacket to snuglyconform to an external geometry of the heart to constraincircumferential expansion of the heart beyond a maximum adjusted volume,surgically closing access to the heart while leaving the jacket inplace, and adjusting the internal volume defined by the jacket after thejacket is in place on the heart using an adjustment mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a normal, healthy humanheart shown during systole;

FIG. 1A is the view of FIG. 1 showing the heart during diastole;

FIG. 1B is a view of a left ventricle of a healthy heart as viewed froma septum and showing a mitral valve;

FIG. 2 is a schematic cross-sectional view of a diseased human heartshown during systole;

FIG. 2A is the view of FIG. 2 showing the heart during diastole;

FIG. 2B is the view of FIG. 1B showing a diseased heart;

FIG. 3 is a perspective view of a first embodiment of a cardiacconstraint device according to the present invention;

FIG. 3A is a side elevation view of a diseased heart in diastole withthe device of FIG. 3 in place;

FIG. 4 is a perspective view of a second embodiment of a cardiacconstraint device according to the present invention;

FIG. 4A is a side elevation view of a diseased heart in diastole withthe device of FIG. 4 in place;

FIG. 5 is a cross-sectional view of a device of the present inventionoverlying a myocardium and with the material of the device gathered fora snug fit;

FIG. 6 is an enlarged view of a knit construction of the device of thepresent invention in a rest state;

FIG. 7 is a schematic view of the material of FIG. 6; and

FIG. 8 is a perspective view of an alternate embodiment of a cardiacconstraint device according to the present invention.

FIG. 9A is a transverse sectional view of a tensioned cardiac constraintdevice according to one embodiment.

FIG. 9B is a transverse sectional view of the device of FIG. 9A in arelaxed state.

FIG. 10 is a perspective view of an alternate embodiment of a cardiacconstraint device according to the present invention.

FIG. 11 is a perspective view of an alternate embodiment of a cardiacconstraint device according to the present invention.

FIG. 12 side elevation view of a diseased heart with an embodiment ofthe device shown in place

FIG. 13 is a side elevation view of a diseased heart with an embodimentof the device shown in place.

DETAILED DESCRIPTION OF THE INVENTION

1. Congestive Heart Disease

With initial reference to FIGS. 1 and 1A, a normal, healthy human heartH′ is schematically shown in cross-section and will now be described inorder to facilitate an understanding of the present invention. In FIG.1, the heart H′ is shown during systole (i.e., high left ventricularpressure). In FIG. 1A, the heart H′ is shown during diastole (i.e., lowleft ventricular pressure).

The heart H′ is a muscle having an outer wall or myocardium MYO′ and aninternal wall or septum S′. The myocardium MYO′ and septum S′ definefour internal heart chambers including a right atrium RA′, a left atriumLA′, a right ventricle RV′ and a left ventricle LV′. The heart H′ has alength measured along a longitudinal axis AA′-BB′ from an upper end orbase B′ to a lower end or apex A′.

The right and left atria RA′, LA′ reside in an upper portion UP′ of theheart H′ adjacent the base B′. The right and left ventricles RV′, LV′reside in a lower portion LP′ of the heart H′ adjacent the apex A′. Theventricles RV′, LV′, terminate at ventricular lower extremities LE′adjacent the apex A′ and spaced therefrom by the thickness of themyocardium MYO′.

Due to the compound curves of the upper and lower portions UP′, LP′, theupper and lower portions UP′, LP′ meet at a circumferential groovecommonly referred to as the A-V groove AVG′. Extending away from theupper portion UP′ are a plurality of major blood vessels communicatingwith the chambers RA′, RV′, LA′, LV′. For ease of illustration, only thesuperior vena cava SVC′ and a left pulmonary vein LPV′ are shown asbeing representative.

The heart H′ contains valves to regulate blood flow between the chambersRA′, RV′, LA′, LV′ and between the chambers and the major vessels (e.g.,the superior vena cava SVC′ and a left pulmonary vein LPV′). For ease ofillustration, not all of such valves are shown. Instead, only thetricuspid valve TV′ between the right atrium RA′ and right ventricle RV′and the mitral valve MV′ between the left atrium LA′ and left ventricleLV′ are shown as being representative.

The valves are secured, in part, to the myocardium MYO′ in a region ofthe lower portion LP′ adjacent the A-V groove AVG′ and referred to asthe valvular annulus VA′. The valves TV′ and MV′ open and close throughthe beating cycle of the heart H.

FIGS. 1 and 1A show a normal, healthy heart H′ during systole anddiastole, respectively. During systole (FIG. 1), the myocardium MYO′ iscontracting and the heart assumes a shape including a generally conicallower portion LP′. During diastole (FIG. 1A), the heart H′ is expandingand the conical shape of the lower portion LP′ bulges radially outwardly(relative to axis AA′-BB′).

The motion of the heart H′ and the variation in the shape of the heartH′ during contraction and expansion is complex. The amount of motionvaries considerably throughout the heart H′. The motion includes acomponent which is parallel to the axis AA′-BB′ (conveniently referredto as longitudinal expansion or contraction). The motion also includes acomponent perpendicular to the axis AA′-BB′ (conveniently referred to ascircumferential expansion or contraction).

Having described a healthy heart H′ during systole (FIG. 1) and diastole(FIG. 1A), comparison can now be made with a heart deformed bycongestive heart disease. Such a heart H is shown in systole in FIG. 2and in diastole in FIG. 2A. All elements of diseased heart H are labeledidentically with similar elements of healthy heart H′ except only forthe omission of the apostrophe in order to distinguish diseased heart Hfrom healthy heart H′.

Comparing FIGS. 1 and 2 (showing hearts H′ and H during systole), thelower portion LP of the diseased heart H has lost the tapered conicalshape of the lower portion LP′ of the healthy heart H′. Instead, thelower portion LP of the diseased heart H bulges outwardly between theapex A and the A-V groove AVG. So deformed, the diseased heart H duringsystole (FIG. 2) resembles the healthy heart H′ during diastole (FIG.1A). During diastole (FIG: 2A), the deformation is even more extreme.

As a diseased heart H enlarges from the representation of FIGS. 1 and 1Ato that of FIGS. 2 and 2A, the heart H becomes a progressivelyinefficient pump. Therefore, the heart H requires more energy to pumpthe same amount of blood. Continued progression of the disease resultsin the heart H being unable to supply adequate blood to the patient'sbody and the patient becomes symptomatic.

For ease of illustration, the progression of congestive heart diseasehas been illustrated and described with reference to a progressiveenlargement of the lower portion LP of the heart H. While suchenlargement of the lower portion LP is most common and troublesome,enlargement of the upper portion UP may also occur.

In addition to cardiac insufficiency, the enlargement of the heart H canlead to valvular disorders. As the circumference of the valvular annulusVA increases, the leaflets of the valves TV and MV may spread apart.After a certain amount of enlargement, the spreading may be so severethe leaflets cannot completely close (as illustrated by the mitral valveMV in FIG. 2A). Incomplete closure results in valvular regurgitationcontributing to an additional degradation in cardiac performance. Whilecircumferential enlargement of the valvular annulus VA may contribute tovalvular dysfunction as described, the separation of the valve leafletsis most commonly attributed to deformation of the geometry of the heartH. This is best described with reference to FIGS. 1B and 2B.

FIGS. 1B and 2B show a healthy and diseased heart, respectively, leftventricle LV′, LV during systole as viewed from the septum (not shown inFIGS. 1B and 2B). In a healthy heart H′, the leaflets MVL′ of the mitralvalve MV′ are urged closed by left ventricular pressure. The papillarymuscles PM′, PM are connected to the heart wall MYO′, MYO, near thelower ventricular extremities LE′, LE. The papillary muscles PM′, PMpull on the leaflets MVL′, MVL via connecting chordae tendineae CT′, CT.Pull of the leaflets by the papillary muscles functions to prevent valveleakage in the normal heart by holding the valve leaflets in a closedposition during systole. In the significantly diseased heart H, theleaflets of the mitral valve may not close sufficiently to preventregurgitation of blood from the ventricle LV to the atrium duringsystole.

As shown in FIG. 1B, the geometry of the healthy heart H′ is such thatthe myocardium MYO′, papillary muscles PM′ and chordae tendineae CT′cooperate to permit the mitral valve MV′ to fully close. However, whenthe myocardium MYO bulges outwardly in the diseased heart H (FIG. 2B),the bulging results in displacement of the papillary muscles PM. Thisdisplacement acts to pull the leaflets MVL to a displaced position suchthat the mitral valve cannot fully close.

Having described the characteristics and problems of congestive heartdisease, the treatment method and apparatus of the present inventionwill now be described.

2. Cardiac Constraint Device

To facilitate a better understanding of the present invention, a cardiacconstraint device will be provided. The cardiac constraint device ismore fully described in commonly assigned PCT Published Application No.WO 00/02500, the disclosure of which is hereby incorporated by referenceherein. In the drawings, similar elements are labeled similarlythroughout.

In general, the device of the invention comprises a jacket configured tosurround the myocardium MYO. As used herein, “surround” means thatjacket provides reduced expansion of the heart wall at end diastole byapplying constraining surfaces at least at diametrically opposingaspects of the heart. In some preferred embodiments disclosed herein,the diametrically opposed surfaces are interconnected, for example, by acontinuous material that can substantially encircle the external surfaceof the heart.

With reference now to FIGS. 3, 3A, 4 and 4A, the device of the presentinvention is shown as a jacket 10 of flexible, biologically compatiblematerial. As used herein, the term “biologically compatible material”refers to material that does not adversely affect the surroundingtissue, for example, by eliciting an excessive or injurious rejectionresponse, inflammation, infarction, necrosis, etc.

The jacket 10 is an enclosed material having upper and lower ends 12,14. The jacket 10, 10′ defines an internal volume 16, 16′ which iscompletely enclosed but for the open ends 12, 12′ and 14′. In theembodiment of FIG. 3, lower end 14 is closed. In the embodiment of FIG.4, lower end 14′ is open. In both embodiments, upper ends 12, 12′ areopen. Throughout this description, the embodiment of FIG. 3 will bediscussed. Elements in common between the embodiments of FIGS. 3 and 4are numbered identically with the addition of an apostrophe todistinguish the second embodiment and such elements need not beseparately discussed.

The jacket 10 is dimensioned with respect to a heart H to be treated.Specifically, the jacket 10 is sized for the heart H to be constrainedwithin the volume 16. The jacket 10 can be slipped around the heart H.The jacket 10 has a length L between the upper and lower ends 12, 14sufficient for the jacket 10 to constrain the lower portion LP. Theupper end 12 of the jacket 10 extends at least to the valvular annulusVA and further extends to the lower portion LP to constrain at least thelower ventricular extremities LE.

Generally, the jacket 10 is adjusted to a snug fit encompassing theexternal volume heart 10 during diastole such that the jacket 10constrains enlargement of the heart H during diastole withoutsignificantly assisting contraction during systole. The amount ofassistance during systole can be characterized by the pressure exertedby the jacket 10 on the heart H during systole. A jacket 10 that doesnot significantly assist contraction during systole will not exertsignificant pressure on the heart H at completion of systoliccontraction.

Since enlargement of the lower portion LP is typically most troublesome,in a preferred embodiment, the jacket 10 is sized so that the upper end12 can reside in the A-V groove AVG. Where it is desired to constrainenlargement of the upper portion UP, the jacket 10 may be extended tocover the upper portion UP.

Sizing the jacket 10 for the upper end 12 to terminate at the A-V grooveAVG is desirable for a number of reasons. First, the groove AVG is areadily identifiable anatomical feature to assist a surgeon in placingthe jacket 10. By placing the upper end 12 in the A-V groove AVG, thesurgeon is assured the jacket 10 will provide sufficient constraint atthe valvular annulus VA. The A-V groove AVG and the major vessels act asnatural stops for placement of the jacket 10 while assuring coverage ofthe valvular annulus VA. Using such features as natural stops isparticularly beneficial in minimally invasive surgeries where asurgeon's vision may be obscured or limited.

When the parietal pericardium is opened, the lower portion LP is free ofobstructions for applying the jacket 10 over the apex A. If, however,the parietal pericardium is intact, the diaphragmatic attachment to theparietal pericardium inhibits application of the jacket over the apex Aof the heart . In this situation, the jacket can be opened along a lineextending from the upper end 12′ to the lower end 14′ of jacket 10′. Thejacket can then be applied around the pericardial surface of the heartand the opposing edges of the opened line secured together after placedon the heart. Systems for securing the opposing edges are disclosed in,for example, U.S. Pat. No. 5,702,343 (corresponding to WO 98/14136), theentire disclosure of both applications being incorporated herein byreference. The lower end 14′ can then be secured to the diaphragm orassociated tissues using, for example, sutures, staples, etc.

In the embodiment of FIGS. 3 and 3A, the lower end 14 is closed and thelength L is sized for the apex A of the heart H to be received withinthe lower end 14 when the upper end 12 is placed at the A-V groove AVG.In the embodiment of FIGS. 4 and 4A, the lower end 14′ is open and thelength L′ is sized for the apex A of the heart H to protrude beyond thelower end 14′ when the upper end 12′ is placed at the A-V groove AVG.The length L′ is sized so that the lower end 14′ extends beyond thelower ventricular extremities LE such that in both of jackets 10, 10′,the myocardium MYO surrounding the ventricles RV, LV is in directopposition to material of the jacket 10, 10′. Such placement isdesirable for the jacket 10, 10′ to present a constraint againstenlargement of the ventricular walls of the heart H.

After the jacket 10 is positioned on the heart H as described above, thejacket 10 is secured to the heart. Preferably, the jacket 10 is securedto the heart H through sutures. The jacket 10 is sutured to the heart Hat suture locations S circumferentially spaced along the upper end 12.While a surgeon may elect to add additional suture locations to preventshifting of the jacket 10 after placement, the number of such locationsS is preferably limited so that the jacket 10 does not restrictcontraction of the heart H during systole.

To permit the jacket 10 to be easily placed on the heart H, the volumeand shape of the jacket 10 are larger than the lower portion LP duringdiastole. So sized, the jacket 10 may be easily slipped around the heartH. Once placed, the jacket's volume and shape are adjusted for thejacket 10 to snugly conform to the external geometry of the heart Hduring diastole. Such sizing is easily accomplished due to the knitconstruction of the jacket 10. For example, excess material of thejacket 10 can be gathered and sutured S″ (FIG. 5) to reduce the volumeof the jacket 10 and conform the jacket 10 to the shape of the heart Hduring diastole. Such shape represents a maximum adjusted volume. Thejacket 10 constrains enlargement of the heart H beyond the maximumadjusted volume while preventing restricted contraction of the heart Hduring systole. As an alternative to gathering of FIG. 5, the jacket 10can be provided with other ways of adjusting volume. For example, asdisclosed in U.S. Pat. No. 5,702,343 (WO 98/14136), the jacket can beprovided with a slot. The edges of the slot can be drawn together toreduce the volume of the jacket.

The volume of the jacket can be adjusted prior to, during, or afterapplication of the device to the heart. In one embodiment, the heart istreated with a therapeutic agent, such as a drug to decrease the size ofthe heart, prior to application of the jacket. In this embodiment, thetherapeutic agent acts to reduce the overall size of the heart prior tosurgery, and the jacket is thereafter applied to the reduced heart.Alternatively, the present invention can be used to reduce heart size atthe time of placement in addition to preventing further enlargement. Forexample, the device can be placed on the heart and sized snugly to urgethe heart to a reduced size. More preferably, the heart size can bereduced at the time of jacket placement through drugs, for exampledobutamine, dopamine or epinephrine or any other positive inotropicagents, or surgical procedure to reduce the heart size. The jacket ofthe present invention is then snugly placed on the reduced sized heartand prevents enlargement beyond the reduced size.

The jacket 10 is adjusted to a snug fit on the heart H during diastole.Care is taken to avoid tightening the jacket 10 too much such thatcardiac function is impaired. During diastole, the left ventricle LVfills with blood. If the jacket 10 is too tight, the left ventricle LVmay not adequately expand and left ventricular pressure will rise.During the fitting of the jacket 10, the surgeon can monitor leftventricular pressure. For example, a well-known technique for monitoringso-called pulmonary wedge pressure uses a catheter placed in thepulmonary artery. The wedge pressure provides an indication of fillingpressure in the left atrium LA and left ventricle LV. While minorincreases in pressure (e.g., 2 mm Hg-3 mm Hg) can be tolerated, thejacket 10 is snugly fit on the heart H but not so tight as to cause asignificant increase in left ventricular pressure during diastole.

The jacket 10 can be used in early stages of congestive heart disease.For patients facing heart enlargement due to viral infection, the jacket10 permits constraint of the heart H for a sufficient time to permit theviral infection to pass. In addition to preventing further heartenlargement, the jacket 10 treats valvular disorders by constrainingcircumferential enlargement of the valvular annulus and deformation ofthe ventricular walls.

3. Jacket Material Generally

Preferably the jacket 10 is constructed from a compliant, biocompatiblematerial. As used herein, the term “compliant” refers to a material thatcan expand in response to a force. “Compliance” refers to thedisplacement per a unit load for a material. “Elasticity” refers to theability of the deformed material to return to its initial state afterthe deforming load is removed.

While-the jacket 10 is expandable due to its knit pattern, preferablythe fibers 20 of the knit are non-expandable. While all materials expandat least a small amount, the individual fibers 20 do not substantiallystretch in response to force. In response to the low pressures of theheart H during diastole, the fibers 20 are generally inelastic. In apreferred embodiment, the Jacket material is 70 Denier polyester. Whilepolyester is presently preferred, other suitable materials includepolytetrafluoroethylene (PTFE), expanded PTFE (ePTFE), polypropylene andstainless steel.

Preferably, the knit is a so-called “Atlas knit” well known in thefabric industry. The Atlas knit is described in Paling, Warp KnittingTechnology, p. 111, Columbine Press (Publishers) Ltd., Buxton, GreatBritain (1970). The Atlas knit is a knit of fibers 20 having directionalexpansion properties. As shown in FIG. 6, the intertwined fibers 20include a plurality of longitudinally extending filaments 30, whereinopposing surfaces of said multi-filament fibers 20 define a cellstructure. The fibers 20 of the fabric 18 are woven into two sets offiber strands 21 a, 21 b having longitudinal axes X_(a) and X_(b). Thestrands 21 a, 21 b are interlaced to form the fabric 18 with strands 21a generally parallel and spaced-apart and with strands 21 b generallyparallel and spaced-apart.

For ease of illustration, fabric 18 is schematically shown in FIG. 7with the axis of the strands 21 a, 21 b only being shown. The strands 21a, 21 b are interlaced with the axes X_(a) and X_(b) defining adiamond-shaped open cell 23 having diagonal axes A_(m). In a preferredembodiment, the axes A_(m) are 3 mm-5 mm in length when the fabric 18 isat rest and not stretched. The fabric 18 can stretch in response to aforce. For any given force, the fabric 18 stretches most when the forceis applied parallel to the diagonal axes A_(m). The fabric 18 stretchesleast when the force is applied parallel to the strand axes X_(a) andX_(b). The jacket 10 is constructed for the material of the knit to bedirectionally aligned for a diagonal axis A_(m) to be parallel to theheart's longitudinal axis AA-BB

The knit material has numerous advantages. Such a material is flexibleto permit unrestricted movement of the heart H (other than the desiredconstraint on circumferential expansion). The material is open defininga plurality of interstitial spaces for fluid permeability as well asminimizing the amount of surface area of direct contact between theheart H and the material of the jacket 10 (thereby minimizing areas ofirritation or abrasion) to minimize fibrosis and scar tissue.

The open areas of the knit construction also allows for electricalconnection between the heart and surrounding tissue for passage ofelectrical current to and from the heart. For example, although the knitmaterial is an electrical insulator, the open knit construction issufficiently electrically permeable to permit the use of trans-chestdefibrillation of the heart. Also, the open, flexible constructionpermits passage of electrical elements (e.g., pacer leads) through thejacket. Additionally, the open construction permits other procedures,e.g., coronary bypass, to be performed without removal of the jacket.

A large open area for cells 23 is desirable to minimize the amount ofsurface area of the heart H in contact with the material of the jacket10 (thereby reducing fibrosis). However, if the cell area 23 is toolarge, localized aneurysm can form. Also, a strand 21 a, 21 b can overlya coronary vessel with sufficient force to partially block the vessel. Asmaller cell size increases the number of strands thereby decreasing therestricting force per strand. In a preferred embodiment, the cell areaof cells in a particular row directly correlates with a cross-sectionalcircumferential dimension of the heart that the row of cells surroundsrelative to other cross-sectional circumferential dimensions. That is,the greater the cross-sectional circumferential dimension, the greaterthe area of the cells in the row of cells directly overlying thatcross-sectional circumferential dimension. By “correlating” cell areawith cross-sectional circumferential dimension of the heart, the cellarea is determined as a function of the cross-sectional circumferentialdimension of the heart. The cell area is determined so that when theweave material is applied to the heart or is shaped into a jacket andapplied to the heart, each cell can widen sufficiently to providedesirable cardiac constraint. Thus, the cell area will be smaller forcells in a row applied over a region of the heart that has a smallercross-sectional circumferential dimension than the cell area of cells ina row applied over a region of the heart having a larger cross-sectionalcircumferential dimension. The appropriate maximum cell area may be, forexample, 1 to 100 mm², typically 1 to 25 mm², more typically 3 to 9 mm².The maximum cell area is the area of a cell 23 after the material of thejacket 10 is fully stretched and adjusted to the maximum adjusted volumeon the heart H as previously described.

The fabric 18 is preferably tear and run resistant. In the event of amaterial defect or inadvertent tear, such a defect or tear is restrictedfrom propagation by reason of the knit construction.

With the foregoing, a device and method have been taught to treatcardiac disease. The jacket 10 constrains further undesirablecircumferential enlargement of the heart while not impeding other motionof the heart H. With the benefits of the present teachings, numerousmodifications are possible. For example, the jacket 10 need not bedirectly applied to the epicardium (i.e., outer surface of themyocardium) but could be placed over the parietal pericardium. Further,an anti-fibrosis lining (e.g., a PTFE lining) could be placed betweenthe heart H and the jacket 10. Alternatively, the fibers 20 can becoated with PTFE.

The jacket 10 is low-cost, easy to place and secure, and is susceptibleto use in minimally invasive procedures. The thin, flexible fabric 18permits the jacket 10 to be collapsed and passed through a smalldiameter tube in a minimally invasive procedure.

The jacket 10, including the knit construction, freely permitslongitudinal and circumferential contraction of the heart H (necessaryfor heart function). Unlike a solid wrap (such as a muscle wrap in acardiomyoplasty procedure), the fabric 18 does not impede cardiaccontraction. After fitting, the jacket 10 is inelastic to preventfurther heart enlargement while permitting unrestricted inward movementof the ventricular walls. Because the jacket 10 is not constructed froman elastomeric material, it does not substantially assist the heartduring systolic contraction.

The open cell structure permits access to coronary vessels for bypassprocedures subsequent to placement of the jacket 10. Also, incardiomyoplasty, the latissimus dorsi muscle has a variable and largethickness (ranging from about 1 mm to 1 cm). The material of the jacket10 is uniformly thin (less than 1 mm thick). The thin wall constructionis less susceptible to fibrosis and minimizes interference with cardiaccontractile function.

4. Adjustment Mechanism

Chronic heart failure is a dynamic syndrome in which cardiac chambersmay change in size and shape. It has been found that use of a cardiacrestraining device, such as the above-described jacket, may stop cardiacdilation or even, under some circumstances, reverse cardiac dilation.Preferably, beneficial reverse remodeling of the heart reduces themaximum cardiac volume of a diseased heart.

If beneficial reverse remodeling of cardiac physiology occurs followingimplantation of a cardiac restraining device, such as theabove-described jacket 10, it may be desirable to have a jacket 10 thatcan be adjusted to respond to the change in cardiac size, or promote thechange in cardiac size, for example, by changing or reducing internalvolume defined by the jacket 10. A cardiac support device ideally wouldhave a capacity to contract in size, so that it maintains intimatecontact with the cardiac surface and continues to provide a finite limitto cardiac expansion and provides support to encourage reverseremodeling.

The invention provides a jacket 10 that defines an internal volume 16that can be adjusted such that the jacket 10 is capable of maintainingintimate contact with the external cardiac surface, even if the cardiacvolume changes (i.e., increases or decreases) following implantation ofthe jacket 10. The invention provides a cardiac constraint device thatincludes a jacket 10 an adjustment mechanism which allows the jacket 10to be adjusted in size either prior to or after implantation. The jacket10 may also be adjusted to actively encourage reduction in cardiacvolume by reducing the maximum adjusted volume of the heart H.Preferably, the cardiac restraint device includes an adjustmentmechanism which is capable of increasing and/or decreasing the internalvolume 16 defined by the jacket 10.

As used herein, the term adjustment mechanism refers to an apparatus orsystem that is adapted, configured and capable of altering the sizeand/or shape of the above-described jacket 10, particularly the internalvolume 16 defined by the jacket 10. Many adjustment mechanisms arepossible. Although some adjustment mechanisms will be discussed indetail below, a cursory overview will be provided at this time.

One type of adjustment mechanism varies the thickness of the cardiacconstraint device to effectively decrease the internal volume 16 definedby the jacket 10. For example, the jacket 10 may be constructed using ahygroscopic polymer which causes the jacket 10 fibers to expand asfluids are absorbed from the surrounding tissue. Alternately, thecardiac constraint device may include a balloon catheter which can beexpanded to effectively reduce the internal volume 16 defined by thejacket 10. Another type of adjustment mechanism cinches the jacket 10material to effectively decrease the internal volume 16 defined by thejacket 10. For example, the adjustment mechanism may include a stayelement and/or a spring tensioning device to pinch or draw together thematerial of the jacket 10. Alternately, the adjustment mechanism mayinclude a specialized material, such as a stimulus sensitive material ora biodegradable material that causes the jacket 10 material to contract,thereby reducing the internal volume 16 defined by the jacket 10. Astill further example is a jacket 10 which includes a biodegradablepolymer matrix 30 in which a substrate structure 31 is embedded.Preferably the substrate structure 31 is formed using a material (e.g.,a shape-changing memory metal such as nitinol) which is tensioned (todefine a volume) prior to incorporation into the polymer matrix.Preferably, the tensioned structure 31 is sized for initial placement onthe heart. (See FIG. 9A) Over time, the size of the heart is reduced(e.g., by reverse remodeling) and the supporting polymer matrix 30 isdegraded. Degradation of the polymer matrix 31 relieves the tension onthe underlying structure 31′ which is then free to relax. (See FIG. 9B)Preferably the relaxed structure 31′ defines a reduced maximum volume(as compared to the tensioned structure) to encourage continued reverseremodeling of the heart. Other adjustment systems or mechanisms mayinclude combinations of the above described mechanisms.

If desired, cardiac volume can be reduced prior to placement of thejacket 10 on the heart or at the time of jacket 10 placement by theadministration of drugs (e.g., dobutamine, dopamine or epinephrine orany other positive inotropic agents) which reduce heart size.Alternately, cardiac volume can be reduced (prior to implantation orafter implantation) by the temporary use of LVADs or chronic pacing. Thejacket of the present invention is situated on the reduced sized heartto prevent enlargement beyond the reduced size.

Preferably the size of the jacket 10 is adjusted within about 1 to about3 months after the jacket 10 is implanted, particularly for thosedevices in which fibrous ingrowth is allowed or promoted (stable fibrousingrowth generally occurs approximately 3 months or less afterimplantation). However, the device may be adjusted after ingrowth (e.g.,after 3 months). Preferably, if the jacket 10 is adjusted more than 3months after implantation, the adjustment is performed slowly over timeto allow time for remodeling of the fibrotic encapsulation of the jacket10. Advantageously, a positive cardiac response to the reduced size ismore likely to be favorable in response to a slow, gradual tensioning,as compared to a rapid decrease in size.

A. Fibrotic Encapsulation

After implantation of the cardiac constraint device such as the deviceof the invention, the fabric of the jacket 10 may become encapsulated bysuperficial fibrosis on the cardiac surface. Fibrotic attachment of thejacket 10 to the cardiac surface can encourage the jacket 10 to maintainintimate contact with the cardiac surface and thus “adjust” the internalvolume 16 defined by the jacket 10 if the heart volume decreases afterthe jacket 10 is implanted. Thus, the fibrotic encapsulation may alsolimit the maximum cardiac volume. The fibrotic layer may even shrinkover time, further contributing to therapy.

If fibrotic attachment is not established between the jacket 10 and thecardiac surface, a decrease in cardiac volume could ultimately result ina loose-fitting jacket 10 that may stimulate a thick late-stagefibrositic layer due to chronic abrasion of the jacket 10 on the cardiacsurface or due to a build up of excessive fibrous tissue between thecardiac surface and the jacket.

Although fibrotic encapsulation may be generally beneficial inmaintaining a reduced cardiac profile, fibrotic encapsulation of thejacket 10 may not maintain a reduced cardiac profile long-term. Thefibrotic layer may gradually expand (similar to expansion of pericardiumduring congestive heart disease) until the maximum cardiac volume isconstrained by the jacket 10.

B. Biodegradable Elements

In one embodiment, at least one biodegradable element, preferably aplurality of biodegradable elements, are incorporated into the jacket 10to maintain a desired first internal volume 16 of the jacket 10.Preferably, the jacket 10 is designed such that, when the biodegradableelement is removed or degraded, the internal volume 16 jacket 10decreases to a pre-determined second internal volume 16. Consequently,as the biodegradable elements degrade in vivo, the internal volume 16defined by the jacket 10 decreases.

As used herein, the term “biodegradable” means that the polymer willdegrade over time by the action of enzymes, by hydrolytic action and/orby other similar mechanisms in the human body. Biodegradable may alsorefer to a material that is “bioerodible,” meaning that the materialwill erode or degrade over time due, at least in part, to contact withsubstances found in the surrounding tissue fluids, cellular actionand/or “bioabsorbable,” meaning that the material will be broken downand absorbed within the human body, for example, by a cell, and atissue.

The biodegradable elements can be incorporated into the jacket 10 asfilaments 30 in the jacket 10 fibers 20, or as fibers 20 themselves.Alternately, a biodegradable matrix can be embedded in intersticesbetween the filaments 30, fibers 20 and/or open cells 23 of the jacket10 material. Other methods for incorporating biodegradable elements intothe jacket 10 include placement of a pre-tensioned structure aspreviously described.

Suitable biodegradable elements include biodegradable synthetic polymerssuch as polylactides, polyglycolides, polycaprolactones, polyanhydrides,polyamides, polyurethanes, polyesteramides, polyorthoesters,polydioxanones, polyacetals, polyketals, polycarbonates,polyorthoesters, polyphosphazenes, polyhydroxybutyrates,polyhydroxyvalerates, polyalkylene oxalates, polyalkylene succinates,poly(methyl vinyl ether), poly(maleic anhydride), poly(amino acids) andcopolymers, combinations or mixtures thereof. Suitable biodegradableelements also include biodegradable natural polymers such as thosederived from corn, wheat, potato, sorghums, tapioca, rice, arrow root,sago, soybean, pea, sunflower, peanut, gelatin, milk, and eggs, forexample. Natural polymers generally include polysaccharides, proteins,poly(nucleic acids), poly(amino acids), and lipids. Polysaccharidesinclude gums, starch, cellulose, etc. As used herein, the term“oligosaccharide” denotes a sugar polymer of from 3 to 15 units. A sugarpolymer having more than 10 units referred to as a “polysaccharide.”Suitable proteins that may be utilized in the present invention includeegg proteins, milk proteins, animal proteins, vegetable proteins andcereal proteins.

C. Hygroscopic Polymers

In an alternate embodiment, the jacket 10, or a portion thereof, isconstructed from a hygroscopic material. According to this embodiment,the hygroscopic material sequesters water from surrounding tissue afterthe jacket is implanted and thus expands. Expansion of the hygroscopicmaterial reduces the internal volume 16 of the jacket 10 such that theinternal surface of the jacket 10 can maintain intimate contact with thecardiac surface, even if the cardiac volume decreases.

Hygroscopic material can be incorporated into the cardiac constraintdevice as filaments 30 in the jacket 10 fibers 20, or as fibers 20themselves (See, e.g., FIG. 6). Alternately, a hygroscopic matrix can beembedded in interstices between the filaments 30, fibers 20 and/or opencells 23 of the jacket 10 material. Other methods for incorporatinghygroscopic material into the device include applying a hygroscopicpolymer coating to the filaments 30 and/or fibers 20 of the jacket 10. Aliner constructed using at least some amount of hygroscopic polymer canbe formed which substantially conforms to the internal surface of thejacket 10.

Examples of hygroscopic polymer(s) include natural polymers such asglycosaminoglycans, for example, hyaluronic acid, chondroitin sulfate,and cellulose and synthetic polymers, such as hydrogels, poly(vinylalcohol), poly(2-hydroxyethylmethacrylate), polyethylene oxide.

D. Stimulus Sensitive Material

In another embodiment, the jacket 10 is constructed, in its entirety, orin part, from a material that changes shape and/or size in response to astimulus. Examples of stimuli include a temperature change (e.g., roomtemperature to body temperature), electric current, ultrasound,radiofrequence (rf), microwave energy, or any other stimulus that couldelicit a change in device shape or size.

A stimulus sensitive material can be incorporated into the device as afilament 30 in the jacket 10 fibers 20, or as a fiber 20 of the jacket10 material. The stimulus sensitive material can be included in thejacket 10 as a stay element in the form of a hoop, coil, V or W shapedelement, or a continuous zig-zag shape oriented circumferentially aboutthe jacket 10.

The size of a jacket 10 (or the internal volume 16 defined by thejacket) constructed from (at least in part) a stimulus-sensitivematerial can be modified by applying energy (i.e. in the form ofelectric current, ultrasound, radio frequency, or microwave energy) tothe jacket 10. In one embodiment, the size of the jacket 10 (or theinternal volume 16 of the jacket 10) can be incrementally modified byapplying a specified quantity of energy multiple times. In anotherembodiment, the energy is applied using a pacemaker (whether or not thepacemaker is also implanted to control cardiac rhythm).

Polyvinylidine fluoride (PVDF), a piezoelectric material, is an exampleof a stimulus-sensitive material. In one embodiment, the jacket 10 isconstructed, in part or in its entirety, from a piezoelectric materialsuch as PVDF. In this embodiment, the shape and/or size of the jacketcan be altered by the application of a low level electric current. Otherstimulus sensitive materials include shape memory alloy elements, suchas nitinol.

E. Stay Elements

In another embodiment, stay elements 51, for example, bands, strings orligatures, are incorporated into the cardiac constraint device.Preferably, the stay elements 51 are positioned circumferentially aroundthe jacket 10 (as shown in FIG. 8). However, it may be desirable in someinstances to align the stay elements 51 with the vertical axis AA′-BB′of the heart H or to position the stay elements 51 obliquely around thejacket 10. The stay elements 51 are preferably positioned within areceptacle 50 placed on the outer surface of the jacket 10. Thereceptacle 50 may be configured as a series of loops (not shown) or anelongate channel or sleeve of material. The receptacle 50 can orient thestay elements 51 in an essentially linear position, or the receptacle 50can orient the stay elements 51 in a variety of configurations, such asa zig-zag configuration, a sinusoid wave configuration or a square waveconfiguration.

In this embodiment, the jacket 10 positions the stay elements 51 and/orthe receptacle 50 on the heart H in the desired location and orientationand the stay elements 51 and/or the jacket 10 prevent the heart H fromexpanding.

In one embodiment, the jacket 10, stay elements 51 and receptacle 50 areconstructed from a biocompatible non-biodegradable material. As usedherein, the term “non-biodegradable” material refers to material thatdoes not appreciably degrade over an extended period. Examples ofnon-biodegradable polymers include non-biodegradable polyester and PTFE.

Alternately, the jacket 10 is constructed from a biodegradable materialwhile the stay elements 51 and the receptacles 50 are constructed from anon-biodegradable material. In this embodiment, the stay elements 51 arepreferably housed within a non-biodegradable sleeve-like receptacle 50that is attached to the jacket 10. Over time, the biodegradable jacket10 degrades and the receptacles 50 housing the stay elements 51 becomeaffixed to the epicardial surface as a result of fibrotic encapsulationand ingrowth.

The receptacle 50 may be constructed from either a porous material or anon-porous material. Preferably, the porous material of the sleeve-likereceptacle 50 is constructed such that host tissue is only capable ofgrowing a limited depth into the receptacle 50 material, thus keepingthe interior surface of the receptacle 50 and stay elements 51 free fromhost tissue. For example, a material with pores large enough for cellsto enter may form the exterior surface of the receptacle, and theinternal surface of the receptacle may be lined with a material havingpores too small for cells to pass through. Because the inner surface ofthe receptacle 50, and the stay elements 51 remain free of fibrousingrowth, the stay elements 51 are easily adjusted after implantation.The tension of the stay elements 51 can be adjusted using simple knots,or a more sophisticated mechanism such as a ratchet mechanism, a ballooncatheter (described below), or a stimulus sensitive material, to allowfine-tuning of the stay element 51 tension.

The above-described jacket 10 incorporating stay elements 51 can beadjusted prior to or after the jacket 10 is implanted (e.g., followingclosure of the patient at the end of surgery). For example, a specialinstrumentation may be provided for contacting the stay elements 51through a minimally invasive procedure. Alternately, a motor, or othermechanical device may be implanted which is capable of tightening thestay elements 51 following implantation. Alternately, the stay elements51 may be constructed using a stimulus sensitive material, as describedabove, such as PVDF or Nitinol.

F. Balloon Catheter

In another embodiment, an inflatable balloon catheter 60 is incorporatedinto the cardiac constraint device. A single balloon catheter 60 ormultiple balloon catheters can be used. In one embodiment, the jacket 10includes at least one balloon catheter 60 positioned along the internalsurface of the jacket 10 and oriented parallel to axis AA′-BB′ of theheart H and at least one, preferably a plurality, of stay elements 51positioned circumferentially around the jacket 10 and balloon catheter60. Inflation of the balloon 60 increases the tension of the stayelements 51 and thereby effectively reduces the internal volume 16defined by the jacket 10. After implantation of the jacket 10, theballoon catheter 60 can be accessed using a connector implanted justbeneath the patient's skin at a convenient location. The connector canbe implanted, before, after or at the time the jacket 10 is implanted onheart H. Alternately, the balloon catheter 60 can be positionedcircumferentially along the interior surface of the jacket 10 or inpre-determined locations on the interior surface of the jacket 10.

G. Spring Tensioning Mechanism

In another embodiment, a spring tensioning device is incorporated intothe cardiac constraint device. At the time the device is implanted, thespring is maintained under tension by a suitable tension-lock mechanism.At a desired time after the device is implanted, the tension-lockmechanism is “tripped” and the spring-tension energy and tension istransferred from the spring to the jacket 10, resulting in reduction inthe internal volume 16 defined by the jacket 10, and relaxation of thespring. Internal, external and/or minimally invasive tripping mechanismscan be used. An example of an external tripping mechanism is a signalingdevice such as an magnet. A minimally invasive tripping mechanism can bea tool that is inserted through an opening in the patient to trip thetension-lock mechanism.

H. Elastic Tensioning Mechanism

In another embodiment, the jacket 10 includes a band 60 (preferably avertical band, i.e., oriented parallel to longitudinal axis AA-BB of theheart H when in use) of elastic material, such as SILASTIC® material(FIG. 10). The vertical band of elastic material 60 allows the jacket 10to be stretched to encompass a diseased heart with an increased cardiacvolume. When the elastic material is not stretched (i.e., relaxed), thejacket 10 defines a volume that approximates the maximum cardiac volumeof a healthy heart. Thus, as the heart undergoes reverse remodeling, theelastic band 60 in the jacket 10 relaxes and the maximum volume definedby the jacket 10 is decreased.

Preferably, the vertical elastic band jacket 10 is constructed using aband of horizontally oriented (i.e., oriented circumferentially aroundthe heart) elastic rods 61. Preferably the rods are generallycylindrical to reduce the effect of fibrosis upon contraction of therods. Alternately, the vertical elastic band 60 may be a solid uniformsheet of elastic material, preferably an elastic material with a smooth,slippery surface is used (to reduce fibrotic adhesions).

I. Vertical Spring Tensioning Device

In an alternate embodiment, the jacket 10 includes a vertically orientedspring tensioning device 55 (See, e.g., FIG. 11). The verticallyoriented spring tensioning device may be constructed, for example, froma plurality of radially positioned, spaced, ribs having a first end,configured to lie proximate the apex 56 of the heart when in use, andsecond end, configured to lie proximate the AV groove when in use. Theribs may be constructed from a material such as nitinol, or other metal,polymer or composite material. The ribs 55 may be fastened to the jacket10 material by a variety of mechanisms, including sutures, loops ofmaterial, elongate tubes of material, or threaded between the fibers 20or filaments 30 of the jacket 10 material. In one embodiment, the firstends of at least a few of the ribs 55 are connected at the apex 56 ofthe jacket 10, which functions as a leverage point.

In an alternate embodiment, the jacket 10 may further include a metal(or other material) ring 57 that fits over the enlarged ventricles andslides into place at the AV groove (See, e.g., FIG. 12). Preferably thering 57 fits loosely around the AV groove and does not apply unduepressure. The ribs 55, described above, preferably extend from the ring57 towards the apex 56 of the jacket 10. The second end of the ribs 55may be fastened to the ring 57 by any suitable means, preferably bywelding the ribs 55 to the ring 57. In this embodiment, other end of theribs 55 (proximate the apex 56 of the jacket 10) preferably remainunfettered.

When in their initial, unloaded position (before installing on the heartH), volume of the jacket 10 defined by the ribs 55 approximates the sizeof a healthy heart (e.g., prior to enlargement due to disease). Wheninstalled onto the enlarged heart, the ribs 55 apply a gentlecircumferential pressure (i.e., towards the axis AX—AX of the jacket 10)on the heart to halt and reverse cardiomegaly.

Generally, the ribs 55 are curved to follow the contours of the externalsurface of the heart H and to snugly fit the heart H at its enlargeddiseased state. Preferably the ribs 55 are shaped such that, when fitover an enlarged diseased heart H, the ribs exert a compressive force.Preferably, the compressive force encourages reverse remodeling of theheart.

As the heart ventricle muscles under go reverse remodeling, the ribs 55maintain pressure on the cardiac surface to encourage continued reverseremodeling, until the heart H size returns to a size that approximatesthe size of an undiseased (i.e., unexpanded) heart H. Once the heartobtains a size that approximates that of an undiseased heart, the ribs55 relax and no longer compress the heart H. Advantageously, thisembodiment provides a continuous compressive force on the heart H thatis not hindered by fibrosis and/or adhesions.

J. Other

In some embodiments, it may be useful to include other elements tofacilitate the size reduction process. For example, a biomaterial thatis known to inhibit fibrous ingrowth or encapsulation may beincorporated into the jacket. Examples of such biomaterials includehyaluronic acid (active ingredient in Seprafilm, a commerciallyavailable film material from Genzyme Corporation), polyethylene glycol(active ingredient in FocalSeal-L, a commercial product from Focal,Inc.), and polyvinylpyrolidone.

In one embodiment, the biomaterial lines all or part of interior and/orexterior surface of the jacket 10. Preferably, the biomaterial ispositioned between the jacket 10 and the epicardial surface to preventfibroblasts from the cardiac tissue infiltrating the jacket 10, therebyinhibiting fibrous ingrowth and encapsulation of the jacket 10. Thebiomaterial can be positioned uniformly along the inner surface of thejacket 10, or only in specified locations along the inner surface of thejacket 10. For example, the biomaterial may only be located between thejacket 10 and an underlying epicardial coronary artery, to facilitateidentification of, and access to these arteries.

Inclusion of a biomaterial in the device is particularly advantageousduring subsequent operations on the heart, for example coronary arterybypass surgery.

From the foregoing, a low cost, reduced risk method and device aretaught to treat cardiac disease. The invention is adapted for use withboth early and later stage congestive heart disease patients. Theinvention reduces the enlargement rate of the heart as well as reducingcardiac valve regurgitation.

What is claimed is:
 1. A cardiac constraint device for treating diseaseof a heart comprising: a jacket of flexible material defining aninternal volume between an open upper end and a lower end; said jacketadapted to be secured to the heart to snugly conform to an externalgeometry of the heart and to constrain circumferential expansion of theheart beyond a maximum adjusted volume during diastole and permitsubstantially unimpeded contraction of the heart during systole; and anadjustment mechanism comprising a piezoelectric material, wherein saidpiezoelectric material is capable of reducing said internal volumedefined by said jacket after said jacket is secured to the heart.
 2. Adevice according to claim 1 wherein said piezoelectric materialcomprises polyvinylidine fluoride.
 3. A cardiac constraint device fortreating disease of a heart comprising: a jacket of flexible materialdefining an internal volume between an open upper end and a lower end;said jacket adapted to be secured to the heart to snugly conform to anexternal geometry of the heart and to constrain circumferentialexpansion of the heart beyond a maximum adjusted volume during diastoleand permit substantially unimpeded contraction of the heart duringsystole; and an adjustment mechanism comprising: at least one stayelement positioned circumferentially around said jacket, wherein said atleast one stay element is configured to cinch said jacket material toeffectively decrease said internal volume defined by said jacket aftersaid jacket is secured to the heart; and at least one receptacleconfigured to receive said at least one stay element and position saidat least one stay element on an external surface of said jacket.
 4. Adevice according to claim 3 comprising a plurality of stay elements. 5.A device according to claim 3 wherein said jacket material comprises abiodegradable material and said stay element and receptacle comprisenon-biodegradable material.